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  <title>Dva Demo</title>
  <script>
      (function (baseFontSize, fontscale) {
          var _baseFontSize = baseFontSize || 100;
          var _fontscale = fontscale || 1;
          var win = window;
          var doc = win.document;
          var ua = navigator.userAgent;
          var matches = ua.match(/Android[\S\s]+AppleWebkit\/(\d{3})/i);
          var UCversion = ua.match(/U3\/((\d+|\.){5,})/i);
          var isUCHd = UCversion && parseInt(UCversion[1].split('.').join(''), 10) >= 80;
          var isIos = navigator.appVersion.match(/(iphone|ipad|ipod)/gi);
          var dpr = win.devicePixelRatio || 1;
          if (!isIos && !(matches && matches[1] > 534) && !isUCHd) {
              // 如果非iOS, 非Android4.3以上, 非UC内核, 就不执行高清, dpr设为1;
              dpr = 1;
          }
          var scale = 1 / dpr;

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          if (!metaEl) {
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              metaEl.setAttribute('name', 'viewport');
              doc.head.appendChild(metaEl);
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          metaEl.setAttribute('content', 'width=device-width,user-scalable=no,initial-scale=' + scale + ',maximum-scale=' + scale + ',minimum-scale=' + scale);
          doc.documentElement.style.fontSize = _baseFontSize / 2 * dpr * _fontscale + 'px';
          window.viewportScale = dpr;
      })();
      if(!window.Promise) {
          document.writeln('<script src="https://as.alipayobjects.com/g/component/es6-promise/3.2.2/es6-promise.min.js"'+'>'+'<'+'/'+'script>');
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